This invention relates to flanged reducer vortex flowmeters. In particular, this invention relates to connecting a vortex flowmeter to a flanged piping system that has a diameter that is larger than the diameter of the bore of the measurement section of the vortex flowmeter.
Vortex flowmeters are used in the industrial process measurement and control field for measuring a flow rate of a fluid. Vortex flowmeters are typically inserted in a flow pipe that carries the fluid to be measured. Industry applications include petroleum, chemical, pulp and paper, mining and materials, oil and gas. The operating principle of a vortex flowmeter is based on a vortex shedding phenomenon known as the von Karman effect. As fluid passes a bluff body, it separates and generates vortices that are shed alternately along and behind each side of the bluff body. These vortices cause areas of fluctuating pressure that are detected by a sensor mounted in the bluff body or downstream of the bluff body. While the frequency of vortex generation is essentially proportional to fluid velocity, this proportionality varies with the conduit Reynolds number. The conduit Reynolds number is a function of the fluid density, the fluid velocity, the fluid losses, and the inside diameter of the conduit.
In piping systems, there is a desire to keep the Reynolds number low in order to reduce power loss in the piping system. This desire to reduce power loss leads to use of larger pipe sizes and lower ranges of fluid flow velocity in the piping system.
In vortex flowmeters, there are limits to the range of flows that are measurable. When flow velocities are below a lower limit of measurable flow, the vortex flowmeter cannot be relied upon to provide an accurate indication of flow.
For these reasons, reducer vortex flowmeters have been developed in which the flowmeter is connected by flanges to a flanged piping system. The diameter of the measurement section of the bore of the flowmeter is smaller than the inner diameter of the pipe section to which the flowmeter is connected. At the upstream or inlet end, the flow passage is reduced or constricted from the piping system diameter to the bore diameter of the flowmeter. At the downstream, or outlet end the diameter of the passage must increase to match the diameter of the piping system downstream of the flowmeter. This is often achieved with a tapering reducer section at the upstream end and a tapering expander section at the downstream end of the vortex flowmeter.